This invention relates generally to the field of bearings with instruments and, more particularly, to bearings with a built-in encoder, where the encoder is an annular component that generates electromagnetic impulses. It also concerns an assembly an comprising such a bearing, and a sensor, where the sensor is a device to detect impulses generated by the encoder, and a vehicle steering system including such a bearing or assembly.
Such bearings are designed to permit, on the one hand, the rotation of a rotating body in relation to a fixed body and, on the other hand, the detection of angular position or speed or a function of such factors. When applied to a vehicle steering system, the system generally includes a steering shaft mounted to rotate in a steering column, as well as a rack and pinion gearbox, the column and the gearbox being fixed in rotation in relation to the chassis of the vehicle. The bearing or assembly may be inserted between the shaft and the column, or even between the shaft and the gearbox.
There already exist known bearings of the type that include a fixed ring, a rotating ring, and rolling elements between them, and in which an encoder is incorporated. In most embodiments, the bearing includes watertight means, the latter being used to support the encoder. For example, document FR 2,717,266, issued to the applicant, describes a device to detect the rotating speed of a roller bearing, which has an encoder component that forms part of the rotating part of the bearing. In that device, the encoder component is combined with the watertight gasket of the bearing.
For some applications, watertight means are not required, and the axial length of the bearing must be limited, the limitation on the size of the bearing thus constituting a constraint on a bulky design. Among such applications, one corresponds to a rack and pinion gearbox of a vehicle steering system. Document EP 856,720 describes an angular steering lock sensor for a steering system, the sensor including a magnet placed on the end of the steering shaft near which the stationary sensor is located.
In that case, the proposed structure, which permits an angular position to be read, is entirely different from those structures proposing integration of an encoder in a bearing. As a result, that embodiment has a number of disadvantages. On the one hand, it requires revision of the sensor support design, for example, the rack and pinion, in order to free the space needed to insert the sensor. On the other hand, the positioning of the sensor on the end of the shaft exposes it to attack from its surroundings, such as splattering from dust, gravel, or mud.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the invention, this is accomplished by providing a bearing with a built-in encoder comprising a fixed ring, a rotating ring designed to be mounted on a rotating body, and rolling components between the fixed ring and the rotating ring. A frame forms, on the one hand, a support for an encoder and, on the other hand, a rigid connecting means between the rotating body and the rotating ring, the rotating ring fitting onto the connecting means, which is designed to be inserted between the rotating body and the rotating ring. The encoder is in the form of an annular means to generate electromagnetic impulses.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.